Cover Index Contents Preface This Technical Reference Manual is intended primarily to assist writers of software for the Amstrad PC1512, although in conjunction with the PC1512 Service Manual it will be of interest to designers of add-on hardware. It is assumed that the reader has a working knowledge of the Industry Standard architecture comprising of an 8086 (or 8088) with DMA, PIT, RTC and Interrupt Controller support chips; plus Colour Graphics Adapter with Floppy Disk, Serial and Parallel Adapters. The information contained herein is largely unique to this document, with the exception of parts of Appendices 1, 2 & 3 which expand on the information contained in the PC1512 User Instructions and the Microsoft MSDOS Reference Manual. Whilst the PC1512 implements a superset of the Industry Standard, this manual makes no attempt to identify those areas of the PC1512 specification which exceed the Industry Standard. Users should, therefore, exercise caution when writing software for a range of manufacturers' PCs and only use the "Lowest Common Denominator" facilities if simple portability is required. © 1986 AMSTRAD Consumer Electronics Plc Neither the whole nor any part of the information contained herein, nor the product described in this manual may be adapted or reproduced in any form except with the prior approval of AMSTRAD Consumer Electronics Plc ('AMSTRAD'). All information of a technical nature and particulars of the product are given by AMSTRAD in good faith. However, it is acknowledged that there may be errors or omissions in this manual. All correspondence should be addressed to: AMSTRAD Consumer Electronics Plc Brentwood House 169 Kings Road Brentwood ESSEX CM14 4EF All maintenance and service on the product must be carried out by AMSTRAD authorised dealers. AMSTRAD cannot accept any liability whatsoever for any loss or damage caused by service or maintenance by unauthorised personnel. This manual is intended to assist the reader in the use of the product, and therefore AMSTRAD shall not be liable for any damage or loss whatsoever arising from the use of any information or particulars in, or any error or omission in, this manual or any incorrect use of the product. Written by Bill Weidenauer, AMSTRAD Consumer Electronics Plc Published by AMSTRAD First Published 1986 MS-DOS(R) is a registered trademark of Microsoft(R) Corporation DOS Plus is a registered trademark of Digital Research Inc AMSTRAD PC1512 is a registered trademark of AMSTRAD Consumer Electronics Plc AMSTRAD is a registered trademark of AMSTRAD Consumer Electronics Plc Unauthorised use of the trademark or word AMSTRAD is strictly forbidden Cover Index Contents Intro Index Section 1 Table of Contents: Section 1 - Hardware 1.0 Introduction 1.1 CPU 1.2 Memory Layout 1.3 Main Board I/O Channels 1.4 Expansion Bus I/O Channels 1.5 DMA 1.5.1 DMA Page Registers 1.5.2 DMA Initialisation 1.6 System Interrupts 1.6.1 Interrupt Levels 1.6.2 Interrupt Controller initialisation 1.6.3 NMI Mask Control 1.7 Programmable Interval Timers 1.7.1 Timer Configuration 1.8 System Status and Control 1.8.1 Port B - System Control 1.8.2 Port A - Status-1 Input/Keyboard Code 1.8.3 Port C - Status-2 Input 1.8.4 Write System Status-1 1.8.5 Write System Status-2 1.8.6 System Reset 1.9 Real Time Clock 1.10 Parallel Printer Port 1.10.1 Printer Data Latch 1.10.2 Printer Status Channel 1.10.3 Printer Control Latch 1.11 Alpha/Graphics Colour VDU Controller 1.11.1 Alpha Display 1.11.2 Graphics Display 1.11.2.1 Graphics Mode 1 1.11.2.2 Graphics Mode 2 1.11.3 VDU Control Registers 1.11.3.1 VDU Mode Control Register 1.11.3.2 VDU Mode Select Register 1.11.3.3 VDU Colour Plane Write Register 1.11.3.4 VDU Colour Plane Read Register 1.11.3.5 VDU Graphics Mode 2 Border Register 1.11.4 VDU Status Register 1.11.5 MC6845 CRTC Emulation 1.11.6 CRTC Display Addressing 1.11.6.1 Mode Mapping Relationships 1.11.6.2 Display RAM Access Overhead 1.11.6.3 Alpha Mode Character Generator ROM 1.12 Floppy Disk Controller 1.12.1 FDC Hardware Conditions 1.13 RS232C Asynchronous Serial Port 1.13.1 Serial Channel Interface 1.13.2 Serial Channel Pin Arrangement 1.14 Printer Parallel Port 1.15 Keyboard Interface 1.15.1 Serial Clock and Serial Data 1.15.2 Keyboard to Main Board Interface 1.15.3 Main Board to Keyboard Interface 1.15.4 Keycodes 1.15.5 Keyboard Connector 1.16 Mouse Interface 1.16.1 Mouse Connector 1.17 Joystick Interface 1.17.1 Joystick Connector 1.18 Light Pen Connector 1.19 Expansion Card Interface 1.20 Video Connector 1.21 Power Connector Section 2 - Firmware 2.0 Introduction 2.1 Power-Up Initialisation and Self Test 2.2 Power-Up Self Tests 2.2.1 Test Procedure 2.2.2 Test Methods 2.2.3 ROS Checksum Test 2.2.4 VDU RAM and VDU Controller Test 2.2.5 Direct Memory Access Controller Test 2.2.6 Programmable Interval Timer Test 2.2.7 Programmable Peripheral Interface Test 2.2.8 Real Time Clock Test 2.2.9 Asynchronous Communications Element Test 2.2.10 Printer Parallel Port Test 2.2.11 Mouse X and Y Count Register Test 2.2.12 System RAM Test 2.2.13 Programmable Interrupt Controller Test 2.2.14 Disk Test 2.2.15 Keyboard Interface Test 2.3 ROS Interrupts 2.3.1 Interrupt 2: Parity Error (NMI) 2.3.2 Interrupt 5: Print Screen 2.3.3 Interrupt 6: Mouse Button Control 2.3.4 Interrupt 8: System Clock Interrupt 2.3.5 Interrupt 9: Keyboard Interrupt 2.3.5.1 Special Key Actions 2.3.6 Interrupt 14: Floppy Disk Controller 2.3.7 Interrupt 16: VDU I/O 2.3.8 Interrupt 17: System Configuration 2.3.9 Interrupt 18: Memory Size 2.3.10 Interrupt 19: Disk I/O 2.3.11 Interrupt 20: Serial I/O 2.3.12 Interrupt 21: Enhanced Function Interrupt 2.3.13 Interrupt 22: Keyboard I/O 2.3.14 Interrupt 23: Printer I/O 2.3.15 Interrupt 24: System Restart 2.3.16 Interrupt 25: Disk Bootstrap 2.3.17 Interrupt 26: System Clock & Real Time Clock 2.3.18 Interrupt 27: Keyboard Break Interrupt 2.3.19 Interrupt 28: External Ticker Interrupt 2.3.20 Interrupt 29: VDU Parameter Table 2.3.21 Interrupt 30: Disk Parameter Table 2.3.22 Interrupt 31: VDU Matrix Table 2.4 RAM Variables 2.5 Non-Volatime RAM 2.6 ROS Messages 2.6.1 Non-Fatal ROS Messages 2.6.2 Fatal Messages Section 3 - Tables 3.1 Language Links 3.2 Processor Memory Usage 3.3 Keyboard and Key Codes 3.4 Asynchronous Communications Element (8250) Registers 3.5 High Performance DMA Controller (8237A-4) Registers 3.6 Programmable Interrupt Controller (8259-A) Command Words 3.7 Programmable Interval Timer (8253) Registers 3.8 Real Time Clock (HD146818) Registers 3.8.1Time Calendar & Alarm Locations 3.8.2RTC Register Locations 3.9 Floppy Disk Controller (uPD765A) Appendices 1 Mouse Software Interfaces 2 MS-DOS System Configuration 2.1 BREAK Command 2.2 BUFFERS Command 2.3 COUNTRY Command 2.4 DEVICE Command 2.5 DRIVPARM Command 2.6 FCBS Command 2.7 FILES Command 2.8 LASTDRIVE Command 2.9 SHELL Command 2.10KEYBUK Command 3 Country Dependent Information for MS-DOS 3.2 4 RS232C Connections 5 Printer Lead (PL-2) Wiring Specification 6 Power Supply Requirements 7 ROM Character Set 8 Keyboard Keycodes 9 Keyboard Layouts 9.1 UK Keyboard 9.2 US Keyboard 9.3 French Keyboard 9.4 German Keyboard 9.5 Spanish Keyboard 9.6 Italian Keyboard 9.7 Danish Keyboard 9.8 Swedish Keyboard Intro Index Section 1 Contents Index Section 2 SECTION 1 - HARDWARE 1.0 Introduction This manual provides a comprehensive description of the AMSTRAD PC1512 hardware and firmware. General information about the PC1512, GEM Desktop and the delivered operating system software is contained in the AMSTRAD PC USER MANUAL. This manual is intended to satisfy the needs of advanced developers who must have access to the various resources available within the PC1512. 1.1 Central Processing Unit (CPU) The CPU is an 8086-2 microprocessor with 1 Megabyte memory addressing capability (See Figure 1.1) running at a clock frequency of 8MHz. The CPU is connected to an on-board 16-bit system memory bus requiring four 125nS timing cycles (T-States) per access resulting in a 500nS memory cycle for 16-bit memory. The CPU is also connected on an on-board 8 bit I/O and memory peripheral bus with a 4 MHz clock, which in turn connects to an external (off-board) expansion bus. Operations on the 8-bit bus automatically incur 125nS wait states as follows: Operation Wait States Bus Cycle 8-bit (Memory) 4 1.0 μS 16 to 8-bit convert (Memory) 12 2.0 μS 8-bit (I/O) 6 1.25 μS 16 to 8-bit convert (I/O) 16 2.5 μS The CPU is configured to run in maximum mode and the instruction set may be optionally extended by the addition of an 8087-2 Numeric Data Coprocessor. The 8087 BUSY output is connected directly to the 8086 NOT TEST input. 1.2 MEMORY LAYOUT The main board memory consists of 512K bytes of system RAM with parity checking and 16K bytes of system ROM without parity checking.